The most significant and effective drug for the treatment of diabetes after the advent of the sulfonyl ureas has been the development of a group of compounds by Takeda, which are the derivatives of 5-(4-alkoxybenzyl)-2,4-thiazolidinediones of the formula (II) (Ref. Chem. Pharm. Bull. 1982, 30, 3580-3600). In the formula (II), V represents substituted or unsubstituted divalent aromatic group and U represents various groups which have been reported in various patent documents. ##STR3##
By way of examples, U may represent the following groups:
(i) a group of the formula (IIa) where R.sup.1 is hydrogen or hydrocarbon residue or heterocyclic residue which may each be substituted, R.sup.2 is hydrogen or a lower alkyl which may be substituted by hydroxy group, X is an oxygen or sulphur atom, Z is a hydroxylated methylene or a carbonyl, m is 0 or 1, n is an integer of 1-3. These compounds have been disclosed in the European Patent Application No. 0 177 353 ##STR4##
An example of these compounds is shown in formula (IIb) ##STR5##
(ii) a group of the formula (IIc) wherein R.sup.1 and R.sup.2 are the same or different and each represents hydrogen or C.sub.1 -C.sub.5 alkyl, R.sup.3 represents hydrogen, acyl group, a (C.sub.1 -C.sub.6) alkoxycarbonyl group or aralkyloxycarbonyl group, R.sup.4 -R.sup.5 are same or different and each represent hydrogen, C.sub.1 -C.sub.5 alkyl or C.sub.1 -C.sub.5 alkoxy or R.sup.4, R.sup.5 together represent C.sub.1 -C.sub.4 alkenedioxy group, n is 1, 2, or 3, W represents CH.sub.2, CO, CHOR.sup.6 group in which R.sup.6 represents any one of the items or groups defined for R.sup.3 and may be the same or different from R.sup.3. These compounds are disclosed in the European Patent Application No. 0 139 421. ##STR6##
An example of these compounds is shown in (IId) ##STR7##
iii) A group of formula (IIe) where A.sup.1 represents substituted or unsubstituted aromatic heterocyclic group, R.sup.1 represents a hydrogen atom, alkyl group, acyl group, an aralkyl group wherein the aryl moiety may be substituted or unsubstituted, or a substituted or unsubstituted aryl group, n represents an integer in the range from 2 to 6. These compounds are disclosed in European Patent No. 0 306 228. ##STR8##
An example of this compound is shown in formula (IIf) ##STR9##
iv) A group of formula (IIg) where Y represents N or CR.sup.5, R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 represents hydrogen, halogen, alkyl and the like and R.sup.6 represents hydrogen, alkyl, aryl and the like, n represents an integer of 0 to 3. These compounds are disclosed in European Patent Application 0 604 983. ##STR10##
An example of this compound is shown in formula (IIh) ##STR11##
Some of the above referred hitherto known antidiabetic compounds seem to possess bone marrow depression, liver and cardiovascular toxicities and modest potency and consequently their regular use for the treatment and control of diabetes is becoming limited and restricted.